THE ENERGETICS OF PHOTOSYNTHESIS 51 



Small vessel 



Va = 9.50 ml I> = 7.00 ml 



K\,^_ = 0.897 mm- A"co. = 1-698 mm- 

 From the four vessel constants it follows that 



A = 6.29 mm- C = - 10.31 mm^ 

 B = 7.73 mm- D = - 14.78 mm- 



According to equations 17 and 1 8 we find 



xo, = 6.29 h' - 1.11> h 

 xco, = - 10.31 h' + 14.78 h 



In an experiment the pressure changes after 60 min illumination were 



for the small vessel: h' = -|-28 mm 

 for the large vessel: h = +12.5 mm 



so that 



;co, - 6.29 X 28 = 7.73 X 12.5 = 80 /il 

 xco, = -10.31 X 28 + 14.78 X 12.5 = -104 ^1 



Hence the photosynthetic quotient is 



7 = XC0.A0. = -104/80 = -1.30 



§ 20 The Use of Carbonate Buffer Solutions 



Instead of aerating with air containing CO., it is also possible to suspend 

 Chlorella in mixtures of carbonate and bicarbonate which furnish the COo 

 necessary for photosynthesis. The amount of COo in such solutions can 

 easily be calculated . The two dissociation reactions of carbonic acid are 



I H2C03?=^H+ + HCO;r 

 II HCO3 ^ H+ + CO3-- 



the equilibrium constants being 



(H+)(HC03-) 



ki = 

 ki\ = 



(H.2CO3) 



(H+)(C032-) 



(HCO3-) 

 or 



K = 



ku (C032-)(H2C03) 



For (H0CO3) we may write (CO2), so that 



^ (HC03-)^ (19) 



^ (C03'-)(C02) 



